Tens of thousands of anti-war demonstrators have marched through London. Many said they felt motivated to express their views even though the fighting has already begun in Iraq.

The protesters included the old and the young, Christians and Muslims and political activists from all the major parties.

What unified them was their belief that the war against Iraq is unjustified, and that they doubt the true motives of President Bush and British Prime Minister Tony Blair.

One of the march stewards, Roy Evans of London, said he doubts Iraqi President Saddam Hussein is hiding weapons of mass destruction. "The only weapons of mass destruction I see at the moment were on TV in Baghdad last night," he said. "It seems like that was doing some pretty massive destruction."

Another marcher was Annie Marjoram of London. She said the United States should not use its fear of terrorism as a justification to attack Iraq. "We have lived with terrorism here for the last 30 years because of the situation in the north of Ireland," she said. "We didn't go and bomb Dublin."

A member of parliament from Mr. Blair's Labor Party, Jeremy Corbyn, said he was marching because he believes the war is illegal. "I'm appalled that this country has illegally gone into war, with no moral authority, no legal authority and in a unilateral action alongside the United States," he said.

The chairman of Britain's Stop the War coalition, Andrew Murray, said the protest was directed at the government, not the British troops. "We mourn the British deaths that have already happened and we believe the British soldiers are really being put in the firing line by a reckless government policy," said Mr. Murray. "But our criticisms are not at all directed against British servicemen and women. It's directed against the government policy that's put them there."

March organizers admitted the turnout was nowhere close to the one million anti-war demonstrators who protested in London in February. But they said Saturday's march was still the biggest ever against a war that Britain was actually participating in.